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Commit e8330d9b authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: support emerg_wr in console device in example launcher.



This is a magic register which causes a character to be outputted: it can
be used even before the device is configured.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent b3e28b65
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+14 −3
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ typedef uint8_t u8;
#include "../../include/uapi/linux/virtio_config.h"
#include "../../include/uapi/linux/virtio_net.h"
#include "../../include/uapi/linux/virtio_blk.h"
#include <linux/virtio_console.h>
#include "../../include/uapi/linux/virtio_console.h"
#include "../../include/uapi/linux/virtio_rng.h"
#include <linux/virtio_ring.h>
#include "../../include/uapi/linux/virtio_pci.h"
@@ -1687,6 +1687,15 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
		goto write_through16;
	case offsetof(struct virtio_pci_mmio, isr):
		errx(1, "%s: Unexpected write to isr", d->name);
	/* Weird corner case: write to emerg_wr of console */
	case sizeof(struct virtio_pci_mmio)
		+ offsetof(struct virtio_console_config, emerg_wr):
		if (strcmp(d->name, "console") == 0) {
			char c = val;
			write(STDOUT_FILENO, &c, 1);
			goto write_through32;
		}
		/* Fall through... */
	default:
		errx(1, "%s: Unexpected write to offset %u", d->name, off);
	}
@@ -2048,6 +2057,7 @@ static struct device *new_pci_device(const char *name, u16 type,
static void setup_console(void)
{
	struct device *dev;
	struct virtio_console_config conf;

	/* If we can save the initial standard input settings... */
	if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
@@ -2075,8 +2085,9 @@ static void setup_console(void)
	add_pci_virtqueue(dev, console_input);
	add_pci_virtqueue(dev, console_output);

	/* There's no configuration area for this device. */
	no_device_config(dev);
	/* We need a configuration area for the emerg_wr early writes. */
	add_pci_feature(dev, VIRTIO_CONSOLE_F_EMERG_WRITE);
	set_device_config(dev, &conf, sizeof(conf));

	verbose("device %u: console\n", devices.device_num);
}